1. Field of the Invention
The invention relates to a development unit and an image forming apparatus using the same.
2. Description of the Related Art
In general electrophotography includes: a charging step of uniformly charging a photoconductive insulating layer; a light-exposure step of exposing the layer to light, and forming an electrostatic latent image by eliminating electric charges on a part of the layer exposed to light; a development step of making the formed electrostatic latent image visible by causing a developer, which includes at least a coloring agent, to adhere to the formed electrostatic latent image; a transfer step of transferring the obtained visible image onto a transfer medium such as a transfer sheet; and a fixing step of fixing the visible image to the transfer medium by heating and pressing, or by any other appropriate fixing method. Incidentally, the development step includes: a developer supplying step of supplying the developer to a developer carrier.
Japanese Patent Application Publication No. 2009-20224 describes a technology for extending the life of a development unit by specifying: a ratio of free external additive added to the developer; a surface roughness of the developer carrier; and a rotational circumferential speed of the developer carrier.